IMAP and POP are separate email protocols that are used by email clients (such as Outlook, Thunderbird, Windows Mail) when downloading emails from a mail server.
There are significant differences between the two protocols and are both designed for different use cases.
POP (Post Office Protocol)
All emails received and sent through this protocol are downloaded directly to the device and are not stored on the mail server. This method allows you to read and access your emails even while you are offline.
Because the emails are stored locally on the device, any damage or issue with the device can pose an extreme risk to the emails.
The POP email protocol is not designed to be used across multiple devices. Reading your emails from multiple computers using POP can result in the duplication and deletion of emails.
The main advantage to using POP is that it uses significantly less server storage as emails are not kept on the server for more than 14 days at a time.
IMAP (Internet Message Access Protocol)
Unlike POP, IMAP keeps your messages on the mail server. When you open an email using IMAP, it loads the message that is stored on the server. IMAP syncs across multiple devices allowing you to organise and view mail in different folders across all devices.
Typically, your email client will cache emails for up to 14 days allowing offline access within that period.
If you plan to view your mailbox from multiple devices, we strongly recommend using IMAP.
Both email protocols have their advantages and disadvantages. What you decide to use is ultimately up to you and your use case.